You might be able to do it with 1 cpu/core for the VM, though there are
reports that guest OS will crash with this setup.
With both cores, you'll get kernel panics on the host OS.
There may be a few T400 laptops with CPUs that work well with hardware
virtualization, but they are rare.
Hardware virtualization is unstable without CPU microcode updates. Libreboot
excludes these, since they are non-free.
You can use software-based virtualization, if you disable the KVM module in
the linux kernel. Xen-based virtual machines should be fine, and offers
decent performance.
